Numbers that are n-gons for three or more n's, where n=3,4,5,...,16.

Terms

a(0) =1a(1) =15a(2) =36a(3) =45a(4) =325a(5) =561a(6) =1225a(7) =1540a(8) =3025a(9) =4186a(10) =11781a(11) =40755a(12) =41041a(13) =58311a(14) =121771a(15) =221445a(16) =1334161a(17) =1413721a(18) =1777555a(19) =3000025a(20) =5785101a(21) =27169506a(22) =36855405a(23) =113123361a(24) =321197185a(25) =1167483681a(26) =1533776805a(27) =1631432881a(28) =2051297326a(29) =2194498125